A liquid dispenser is mounted on a container and has a shell, a spout assembly, an injection assembly, a power pack and an activating assembly. The shell is mounted on the container and has an injection tube. The spout assembly is formed on and protrudes from the shell. The injection assembly is mounted in the shell pumps air into the injection tube to force liquid from the spout assembly. The activating assembly selectively activates the injection assembly and selectively seals or opens an air passage to the injection tube.